1. Field of the Invention
The present invention relates to a hand-held type printer and, more particularly, to a scan control circuit for detecting a stable scanning movement of the hand-held type printer over a copy paper.
2. Description of the Prior Art
According to a prior art hand-held type printer, a scan control circuit is provided which includes an encoder having a rotating element for producing pulses in response to the rotation of the rotating element effected by the sliding movement of the hand-held type printer over a copy paper or the like. The number of pulses produced from the encoder corresponds to the scan distance of the printer over the copy paper. By the number of pulses produced from the encoder, the timing for starting the printing operation is determined. Also, according to the above-noted prior art hand-held type printer, the number of pulses generated relative to the scanning is counted, so that when the counted pulse amount reaches a predetermined amount, it is assumed that the scanning operation is stable and, thereupon, power is turned on to start the printing operation.
However, the rotating element may be undesirably rotated when the printer receives impact or is imparted a shaking motion, such as when the printer is picked up or when it is placed on a desk. In such a case, the encoder may produce pulses, notwithstanding that the printer is not actually making any scanning movement over a copy paper. When such false pulses are produced before the start of the copying operation, the power may be turned on too early, i.e., before the printer acquires a stable scanning movement Accordingly, the printed images may be deformed or may be printed with improper darkness.